Telephone switch



March 19, 1940.

FIG. 3

K. MULLER rsuarnons swr'rcn Filed Sept. 21, 1936 FIGJ 2 Sheets-Sheet 1 FIG. 4

INVENT OR. KONRAD MULLER ATTORNEY.

March 19, 1940.

K. MULLER TELEPHONE SWITCH- Filed Sept. 21, 1936 FIG.5

2 Sheets-Sheet 2 KO RAD MULLER INVENTOR.

ATTORNEY.

Patented Mar. 19, 1940 UNITED STATES @FFiCE TELEPHONE SWITCH Application September 21, 1936, Serial No. 101,825 In Germany September 26, 1935 2 Claims.

The subject of the invention is a rotary selector, more especially for use in telephone systems, of the type in which the wipers associated with the speaking leads remain out of contact with the bank contacts while the switch is being set.

By means of the free movement of the stepping wipers of such selectors a reduction is eifected in the noise made by the selector and furthermore the wipers are exposed to less wear.

A further advantage of such switches consists in that the wipers associated with the speaking leads and the bank contacts associated with these wipers can be provided with expensive noble metal contacts thereby producing greater efficiency in contacting.

According to the invention it is proposed to efiect the raising of the wipers associated with the speaking leads from the bank contacts by a magnet, while the wipers are pressed into engagement with the contacts by means of a spring which is subjected to tension by this magnet. Thus, in contradistinction to the known proposals of this sort, the wiper magnets are only brought into use for a short time, namely, only during the relativeiy short time occupied by the setting and releasing motions, the smallest number of additional means being necessary.

The invention is represented by way of embodiment in Figs. 1 and 2 of the drawings. Fig. 1 shows the arrangement in the rest position and Fig. 2 shows the operating position. In the figures only those parts of the set are shown which are necessary to enable the invention to be understood.

Fig. 3 shows a particular construction of the wipers associated with. the speaking leads at the ends which contact with the bank contacts.

Fig. 4' shows a guarding device in the wiper set for preventing the wipers being displaced by hand 40 when the wipers associated with the speaking leads are in contact with the bank contacts.

Fig. 5 shows a circuit for such a switch provided with a wiper magnet which is motor driven and operates as a group selector.

The switch shown in Figs. 1 and 2 comprises the wiper set which is displaceably mounted on the shaft l and is set in rotation over a toothed disc 2 by the driving wheels 3 of a driving mechanism which is not shown. The wipers i of the 50 wiper set represent the wipers associated with the speaking leads and as may be seen from Fig. 3 are slotted at the working end in the same way as a relay spring and are provided with double contacts 5 formed of noble metal. The other wipers 6 of the wiper set are constructed as double wipers in the'usual way. Only a part of the contact bank which is indicated by the reference l is shown. All the bank contacts 8 which are associated with the wipers 4 connected to the speaking leads likewise possess contacts 9 formed of noble metal arranged at the point which make contact with these wipers.

At the lower side of the plate in of the-selector which carries a switching shaft i an electromagnet is arranged which will be referred. to in the following description as the wiper magnet BU. It is constructed as a flat relay in order to produce a compact arrangement having satisfactory magnetic properties, being provided with a flat core and an armature ll arranged laterally with respect thereto. The armature carries a bent member L2 to whose upper portion is attached a spring it which is mounted on the upper surface of the plate [0. If a different mounting is preferable the spring can, of course, consist for example, of a helical spring. The bent member I2 is pressed against a disc l4 rigidly fixed to the wiper set when the wiper magnet is deenergized so that the wiper set which is displaceably mounted on the shaft 1 is displaced as far as the disc [5 at the upper end of the shaft 1, which disc forms a stop in the normal condition of the switch (Fig. 1) i so that the wipers 4 associated with the speaking leads move from their normal position and at their noble metal contacts 5 press against the bank contact strips 8 which are similarly provided with noble metal contacts 9. The double wipers 8 of the wiper set accompany this displacement on account of their spring attachments.

When the switch is being set the wiper magnet BU is energized. The armature l l when attracted carries with it the bent member l2 against the pressure of the spring l3 and thereby releases the wiper set. Accordingly, the wiper set can now drop down while it is pressed by the current conducting springs !'3 of the wiper against the bush IT at the lower end of the shaft I (Fig. 2). At the same time, on the energizing of the wiper magnet BU contact I Ebu is operated by the armature H whereby the circuit for the driving device of the selector is completed or prepared. Since the wipers i associated with the speaking leads are already out of contact with the bank contacts 8, the wipers can move freely between the bank contacts during the rotary movements which now take place without a loop being established between the points of contact 5 and the contact strips 8. The pressure of the spring l3 against the wiper set is removed by the attracted armature II of the wiper magnet BU so that the wiper set rotates without any particular friction. The friction occurring at the bush I! and the shaft I is small since only a portion of the guiding springs I6 operate on it.

When the switch is brought to rest after the wiper has found a free line the wiper magnet BU is again de-energized so that the spring I3 which is subject to tension in the operated posi tion of the armature II returns the wiper set to the original position in which the points of contact 5 of the wipers 4 are pressed against the corresponding bank contacts 8 (Fig. 1).

When the switch is released the wiper magnet BU again energizes and it repeats the process already described of removing the wipers associated with the speaking leads while at the same time switching on the driving device, until the selector has reached the rest position where on account of the deenergizing of the Wiper magnet BU the wiper set again takes up the position shown in Fig. 1.

In order to prevent the wiper set from being displaced by hand in this position a locking tooth I8 (Fig. 4) is arranged on the base plate I I] of the selector and engages with the teeth of disc 2 of the wiper set when this is in the elevated position. When the wiper magnet BU energizes the toothed wheel 2 is displaced together with the wiper set on the shaft I so that the locking tooth I8 disengages with the teeth so that only now when the wiper set is in a position to allow the wipers associated with the speaking leads to move freely between the bank contacts can the switch be rotated by the driving mechanism.

In Figure 5 is shown the circuit arrangement of the switch showing the wiper magnet and the driving arrangements. The switch shown operates as a group selector. The switch can, of course, also be used in the same way in other switch stages of telephone systems. The mode of operation is as follows:

In describing the mode of operation of the switch special importance is given to the manner in which the wiper magnet is operated. Details which are irrelevant to the fundamentals of the present case are omitted.

The motor switch provided with a wiper magnet BU has wipers a, b, c, and d. Of these wipers a and b are moved by the wiper magnet BU so that when the switch is stepped they do not contact with the bank contacts. The wipers c and d travel over their associated contact banks. When a free line has been found the wiper magnet releases and wipers a and b switch the line through. The motor is connected up by the wiper magnet BU. Any rotation of the switch with the a and b wipers not withdrawn is thus definitely prevented. BU is only transitorily energized on the setting and release of the switch. The motor driven switch which operates as a group selector may be seized by a switch in the preceding switching stage, when relay C energizes in the following circuit: earth, battery, winding II of relay C, rotary off-normal contact Iw, earth in the preceding switch. Relay C, at contact 20 breaks the short-circuit over its winding I and locks up by closing contact 30 in a circuit independent of Iw. The energizing of relay C opens contacts 50 and 60, contact 'Ic being then closed. This operation of the contacts has for the moment no influence on the switch. It will be assumed that one setting impulse is transmitted to the switch. The switch will then search for a free-line in the first 's level. By the setting impulses relay A which is provided with windings I, II and III is energized over the following circuit: earth, battery, resistance Wi, contact 4w, winding I of relay A, a lead, earth in the preceding switch. At this contact 8a, relay A opens the shunt around winding II of relay V and by closing contact 9a the circuit is closed for both windings of relay V. The closing of contact Illa and the opening of contact IIa has no effect for the moment. The circuit of relay V runs are follows: earth, battery, windings I and II of relay V, rotary offnormal contact IZw, contact 9a, winding I of the repeater for the busy signal and earth. Relay V energizes in this circuit and shunts contact I210 in this circuit by contact I311. By the opening of contact I51) and the closing of contact I41), the following circuit is closed for the wiper magnet BU: earth, battery, wiper magnet contact I41) and earth. The wiper magnet energizes in this circuit and closes its contact Ifibu and accordingly completes the circuit for the energizing winding MII of the driving motor of the switch. This circuit runs as follows: earth, battery, winding MII of the motor, cam contact IInlc, contacts Itbu, I41) and earth. Current passes through winding MII and the armature of the motor is thereby moved as is also the switch. motor operates in the known way in that the nk contacts are controlled from its shaft and thereby alternatively subject the windings MI and MII of the motor to current. Wiper d of the switch moves out of the zero position into position I. In this position in addition to winding MI of the motor which is then connected up over contact I8nlc, winding MII is energized in the following circuit: earth, battery, winding MII, contacts Ilia, position I of the switch, wiper d, contacts Ifibu, I41), and earth. Since both the energizing windings of the switch are subjected to current the switch is brought to the rest position in the known way. When relay A falls back after the numerical impulse, contact Illa is opened and contact IIa closed. Through the opening of contact Illa the circuit for winding MII is broken and the motor is switched on until in position 2 the following circuit is set up for winding MI: earth, battery MI, contacts Ha, 201:, 1c, wiper d in position 2, contacts I (ibu,

I41) and earth. In this position the line of the group in question is already closed. Not all the contacts in the switch levels are shown but only the important ones which play a part in the controlling of the switch within a group. After the impulse or after an impulse train relay V falls back in the known way. When a number of impulses are transmitted relay V works as a slow acting relay on account of the short circuit established over contact 8a and accordingly holds up throughout the impulse train. Over contacts 181) the damping windings MII, MI of the motor are connected up.

These windings are provided in order to enable the motor to run more slowly during the indi vidual steps. Through the release of relay V testing potential is applied over contact I51 by way of earth, contact 2520. contacts Eli?) and 28122 and the winding of relay PI to wiper c of the switch. If the line is free, i. e., if battery potential is encountered, relay PI energizes in this circuit. On account of the opening of contact I41; the wiper magnet EU is deenergized for a short time but is then again subjected to current over the following circuit: earth, battery, EU,

contact I522, Ma, 28172, 23v, 2510, earth. Relay Pl over its contact 4011! establishes a shunt over winding MI and M11 of the motor and thereby brings the motor to rest. Relay Pl in addition connects up windings I and IE of the second testing relay P2 to wiper c of the switch over its contact 36171. Reiay P2 is accord ngly connected up in parallel with relay Pi and energizes in the circuit described on account of battery on a free line in the next switch. The line seized is guarded against seizure on the part of another switch in the known way by the closing of contact 3 I 22. Relay Pi is disconnected by the opening of contact 21 92 and the closing of contact Mp2. The wiper magnet EU is disconnected by contact 23102 so that wipers a and b are brought into contact with their contact hank. Contact 28192 disconnects the motor. The call is switched through at contacts 35312 and Bfipil.

When conversation is completed the switch is released in the following way:

When the calling subscriber replaces the receiver the circuit for the seized relay C is broken. Belay C accordingly falls back. The closing of contact 50 establishes the following circuit for relay V earth, battery, winding I of relay V, contacts Ba. 50, 251/), earth. Relay V energizes in this circuit and at contact MU again completes a circuit for the wiper magnet BU. Over this circuit the motor is transitorily con nected up again.

The circuit for the motor is completed over contact lBbu'. Since relay Pl has released the switch is stepped on by the motor. The switch ravels to the zero position and is there brought to rest. Since relay C is deenergized contact 60 is now closed so that in addition to winding MII to which current is applied in the zero position of the switch winding MI is connected up in the following circuit: earth, battery, winding MI, contacts Ho, 2%, wiper d in position 0, contacts Hibu, I412, earth. Through the opening of contact 25w relay V makes a delayed release. Relay V again disconnects the motor.

Positions 5 and l of the switch are dead positions. If the switch has found no free line in the selected group it passes to position 4 or 7 dependent upon the group in which the switch is searching It is here brought to rest since in addition the winding MI of the switch which is then connected up over contact itnk, winding of MII is energised in the following circuit: earth, battery, winding MII, contact iiilo. winding 11]. of relay A, wiper d in position i or 1, contacts lfibu, I51) Ma, 28112, 261;, 25w, earth. In this circuit relay A also energizes and at contact lla disconnects the wiper magnet BU. Relay A locks up in the following circuit: earth, winding 1 of busy tone transformer, contacts 9o, Mp2, winding II of relay A, winding E1 of relay A, contacts 5G1], winding MII of motor, battery earth. Over relay A the busy signal is ransmitted by induction to the calling subscriber. Contacts title and 6 h) are closed while contact 520 is open.

The wiper magnet BU can be provided with further other contacts efifecting other switching operations. Thus for example the wiper magnet can be connected up by the seizing relay and relay A can be connected. to the a-lead over a contact of the wiper magnet. Moreover, it is possible to do away with the switching through contacts (35:02 and Slipfi) and to effect the switching through directly by the disconnection of the wiper magnet and thereby through the a and b wipers.

What is claimed is:

1. In a non-numerical switch, a wiper set for said switch, bank contact sets accessible to said wipers, means for driving said wipers past said bank contact sets, a magnet and armature therefor, an energizing circuit for said magnet com.- pleted when the switch is seized, contacts controlled by the energization of said magnet for closing an operating circuit for said driving means, and means also controlled by the energization of said magnet for preventing said wipers from engaging said bank contact sets while the wipers are being controlled by said driving means.

2. In a non-numerical switch as claimed in claim; 1, a set of test bank contacts, a test wiper controlled by said driving means to be advanced over successive contacts in said test bank, a test relay, a test circuit including said relay said test wiper and a particular one of said test contacts, means controlled by the energization of said test relay over said test circuit for disconnecting the energizing circuit for said magnet.

KONRAD MiiLLER. 

